My invention pertains to static converters for use particularly in high voltage applications. More specifically, the invention pertains to a static converter arrangement which includes a resonant regulating element, an output level detector, and a control circuit for varying the operating frequency of the inverter to regulate the output voltage.
Under certain types of use, static voltage converters must meet predetermined specifications as to output levels. For example, static device converters used on board railroad vehicles, particularly electric locomotives, must provide essentially constant output voltage in spite of appreciable variations in direct current input voltage and load requirements. Various arrangements to stabilize the converter output characteristics have been proposed and used, e.g., the so-called chopper devices. All these arrangements have disadvantages and operational difficulties. For example, switching losses in chopper devices increase greatly as input voltage rises. Also harmonic components fed back to the source, i.e., a railroad electric distribution system, become large at high voltages. Thus an improved regulation means for static converter apparatus is a pressing need.
Accordingly, an object of my invention is to provide converter apparatus capable of maintaining substantially constant output characteristics over large variations in the direct current input voltage with substantially constant energy transfer.
Another object of the invention is a static converter supplying, from a source of direct current voltage which may vary over considerable range, a substantially constant output voltage of a different level.
A still further object of my invention is a static converter arrangement with an inverter network having two branches with controlled static switching means alternately actuated to conducting condition by a control circuit means which sets the inverter frequency by the triggering rate of the static devices, and which further includes regulator means in the inverter output circuit to vary the load voltage level as the frequency of the output varies and a level detector means to vary the triggering rate of the control circuit means as variations in the output voltage are detected.
Yet another object of the invention is a high voltage inverter arrangement with an output regulator means for peaking the output voltage at the resonant frequency of the regulator, a level detector for sampling the output voltage level, and a feedback signal network for applying a signal, in accordance with any detected variation in the output level, to the inverter control for varying the trigger frequency of the controlled static switches of the inverter to adjust the output voltage to a predetermined level.
Other objects, features, and advantages of the invention will become apparent from the following description and appended claims when taken with the accompanying drawings.